Explosion of a hot-oil circuit as a consequence of process, plant engineering and management shortcomings

On June 3, 1993, an explosion occurred at the Mediterranea refinery, in Milazzo, Sicily. Seven people died and eighteen people were injured with burns. An explosion in the accumulation tank 27V-16 involved hot-oil circuits subserving the refining units Topping 3, Topping 4, and HDT-RC. The explosion was caused by a sudden overpressure in the 27V-16 tank, probably as a result of the sudden vaporization of a small quantity of water. Shortcomings in the process design and in the management were at the origin of the accident, in particular: Some process choices undertaken a couple of years before the accident, such as the use of gas oil from a Topping column in place of diathermic oil and the use of a combustible gas in place of nitrogen. Some operational mistakes in the 13F-2 oven conduction and the failure (or inadequacy or exclusion) of control systems or automatic and manual safety devices. A detailed Fault Tree connects the process, design and management shortcomings identified.